The present invention relates to high voltage electrical apparatus. The invention is particularly applicable to electrical apparatus useful as an electromagnetic pulse (EMP) simulator, and is therefore described below with respect to this application.
As well known, a nuclear explosion generates an intense electromagnetic pulse (EMP) reaching amplitudes of tens of kilovolts per meter with a rise time of few nanoseconds. Such EMP's can disable or damage electronic and electrical equipment unless the equipment is protected, or "hardened", against such EMP's. Similar EMP s can be generated by lightening in nature. Accordingly, EMP simulators have been developed to simulate the effects of such EMP's in order to test their effects on electrical and electronic equipment.
One form of EMP simulator includes two large-area electrodes mounted in spaced relation, and a high-voltage generator electrically connected to the two electrodes to apply a high-voltage pulse between them. The equipment to be tested is placed between the two electrodes in order to test how the simulated EMP affects the equipment operation. The high-voltage pulse applied to the two electrodes is in the order of one megavolt, and the rise time is extremely fast, in the order of 5 nanoseconds.
Such a large voltage pulse requires a relatively large spacing between the electrodes in order to avoid arcing. However, a large spacing between the two electrodes increases the inductance of the electrical curcuit, thereby increasing the rise time. For this reason, EMP simulators of this type usually include electrical connections between the high voltage generator and the two electrodes enclosed which are within a housing filled with an insulating gas under pressure.
Because of the required spacing between the two electrodes at their point of connection to the high-voltage generator, a very large housing is generally required which is filled with the insulating gas under pressure. Such a construction is not only space-consuming but also very expensive, because of the large amount of insulating gas required to fill the enclosure under pressure. Moreover, the insulating gas commonly used is a halogenated gas (e.g. "Freon"), which has been found to create serious ecological problems. Further, the large size of the housing to be filled with the insulating gas greatly limits the pressure that can be safely used.